Generally, systems for managing power distribution systems manage a power distribution system, under constraint conditions in which a power distribution system has no separate power supply except active and reactive power (MW/MVAr power injection) supplied from a transmission network, and the power distribution system must maintain a radial structure. As shown in FIG. 1, a conventional system for managing a power distribution system includes a DMS server 10, a feeder FEP 20, a DG FEP 30, a station FEP 40, an AMR 45, an FM 46, a CIS 47, a distribution system managing database 52, a real time database 54, a control database 56, a history database 58, an operator terminal 60, a GIS server 70, a history server 80 and a simulator 90 which are connected to each other through a network. The DMS server 10 is connected to the feeder FEP 20 which is connected to a plurality of distribution automation terminal devices (22; feeder remote terminal units; hereinafter, referred to as FRTUs), the DG FEP 30 which is connected to a plurality of DG RTUs 32, and the station FEP 40 which is connected to a plurality of station RTUs 44. The DMS server 10 stores data obtained from the Feeder FEP 20, the DG FEP 30 and the station FEP 40. The DMS server 10 uses the obtained data to detect occurrence of a fault of the power distribution system and uses a fault indication signal (hereinafter, referred to as an FI signal) to restore the fault. The DMS server 10 manages a distribution system managing database 52 which stores distribution system managing data including contraction data, customer data, equipment data, a base map, etc., a real time database 54, a control database 56, a history database 58, etc.
The FRTUs 22 are connected to the feeder FEP 20. The feeder FEP 20 obtains conditions (analog and digital) from the different kinds of FRTUs 22 and transmits them to the DMS server 10.
The operator terminal 60 transmits an alarm to an operator through an HMI (human machine interface). The operator detects a location where the fault occurs based on the alarm. If a fault occurs between an automatic switch B and an automatic switch D which are disposed between the FRTU A and the FRTU B of the power distribution system, FI signals are transmitted from the FRTU A and the FRTU B, and protective devices such as a circuit breaker, recloser, etc. remove the fault of the power distribution system. The operator remotely opens the automatic switch B and the automatic switch D and separates the fault point from the system. After the fault section has been separated, the operator changes over a normal section in a power failure section to a peripheral line so that power supply can be continued.
In the conventional system for managing the power distribution system, with regard to a fault of the power distribution system, an inflow value of a power transmission system is only one of fault current, and a current inflow path is a single flow path. Therefore, as shown in FIG. 2, in the case where the operation of the protective devices is normal, a protective device which is disposed at a higher level than the fault point is used to remove the fault. The operator opens switches provided at a point B and a point C to separate the fault section from the system. In addition, the operator changes over a load disposed below the point C to a peripheral line so that power can be continuously supplied thereto. A fault current removal method of the protective device includes protection coordination using operation time difference generated by overcurrent relaying. Furthermore, except in a special case, setting a current relay is conducted when the current relay is installed.
In the conventional system for managing the power distribution system, a system fault restoration process is as follows. When a fault occurs, an FI signal is transmitted in an event signal form from the FRTU 22 to the operator. The operator determines a fault section based on the FI signal.
As shown in FIG. 3, the conventional system for managing the power distribution system is configured such that current system conditions are determined by measuring voltage/current/phase at locations at which the automatic switches are installed. As shown in FIG. 4, because there are constraint conditions in which the power distribution system must always be operated in a radial form, voltage and power flow of sections between the installation points of the automatic switches can be inferred only by measuring voltage and power flow at the installation points of the automatic switches. This can be embodied only by the intuition of the operator. However, such measurement data is necessary to be synchronized, and it is very difficult to check detailed system conditions using only partial data.
The conventional system for managing the power distribution system is configured in such a way that system conditions are checked only by judgment (intuition) of the operator without conducting real time system analysis and control. Therefore, in the case where there is a change in the equipment database because of, for example, a change in equipment of the system, it is required to restart the system so as to change the real time database 54. As a result, the availability of the management system is reduced.
Recently, in management of the power distribution system, due to distributed power supply applied to the power distribution system, the above two kinds of constraint conditions may not be always satisfied.
Given this, as shown in FIG. 5, if a fault occurs between points B and C, fault open paths If2 and If3 derived from the distributed power supplies are added, as well as, fault current If1 supplied from the transmission network. Therefore, as in the conventional system, even if the protective device of the point B is operated by overcurrent relaying, because the fault current paths derived from the distributed power supplies remain, removal of the fault is not completed. Furthermore, unlike the transmission network, given the characteristics of the power distribution system in which changes in system topology (changes in conditions of junction switches) frequently occur, use of a fixed protection coordination correction values may cause a problem.
In the conventional system for managing the power distribution system, when a fault occurs, a plurality of FI signals are transmitted to the operator at the same time. In the FI signals, FI signals generated by an error are contained. This problem is further complicated by the distributed power supplies applied to the system. Therefore, it is difficult for the operator to intuitionally determine a fault section based on the FI signals and restore the fault section as in the conventional technique.
Furthermore, as shown in FIG. 6, in the conventional system for managing the power distribution system, conditions such as voltage, power flow, etc. of the system are frequently changed by changes in a generation rate and a load because of the distributed power supplies applied to the power distribution system. Therefore, if only voltage and power flow values of automatic switches of some points are used, it is difficult for the operator to intuitionally estimate voltage and power flow conditions of the remnant sections.
In addition, in the conventional system for managing the power distribution system, to prevent the intuition of the operator to determine the conditions of the system from being reduced because of the distributed power supplies applied to the system, real time system analysis is required. For this, a data supply structure for real time management is necessary. However, the conventional technique is problematic in that the system must restart to change the database 54.